Well, it turns out that Canon is making their own sensor for the Canon EOS R3 after all. After a wording change on various Canon websites last month suggested that it was designed by them but manufactured by somebody else – possibly Sony – Canon has done something they almost never do. They’ve publicly addressed a rumour.
As well as the wording change, an interview with Canon Russia’s Head of Product and Consumer Expertise, Andrey Tischenko by Russian photography website PhotoWebExpo points out that the first Canon camera to contain a stacked sensor was the G7X Mark III – which contains a Sony sensor. But now Canon has confirmed that no, Sony isn’t making the EOS R3 sensor. They are.